Bit patterned media (BPM) and discrete track media (DTR) are becoming more popular media for storage because of their inherent abilities to store more data in a smaller area. The goal of BPM and DTR and other patterned media is to increase bit density. However, manufacturing methods for BPM and DTR are complicated, expensive and inconsistent.
BPM media are typically formed by using lithography to define the pattern on the media substrate. Once the pattern is defined, the translation of the pattern to the media substrate is typically an additive or subtractive process. An additive process, e.g., electrodeposition and lift-off, requires steps of creating a resist pattern and then depositing a magnetic film layer. In contrast, the subtractive process begins with the deposition of a magnetic film layer followed by resist patterning. The resist pattern may serve as an etch mask such that the surrounding magnetic film may be removed by ion milling, reactive ion etching (RIE), wet chemical etching or other processes. An issue with these types of etching is that they are not very selective in defining magnetic and non-magnetic regions on the magnetic film layer. As a result, etching does not always result in consistently higher bit densities.
Other methods have been reported with varying results. For example, focused ion beams (FIB) poisoned with gallium (Ga+) have been used in order to created discrete magnetic islands (also referred to as “dots” or “bits”) smaller than 70 nm in diameter. However, magnetic film layer modification using FIB is not readily scalable to mass production.
What is therefore needed is a way to define discrete magnetic and non-magnetic regions on a magnetic film layer that is both efficient and scalable to mass production.